>   MIC3287 based white led driver driving a chain of 6 white LEDs (yes,
> some sort of rechargeable torch)

Not the main focus of your post, but

Datasheet  http://www.micrel.com/_PDF/mic3287.pdf

1.2 MHz and 350 mA switch are  good but seems not to live up to promise.
I was surprised at how inefficient it is at lower currents.
Under 80% across the shown range.
Digikey ~ $US0.57 in 24,000 quantity, suggesting it is never super
cheap even  from lowest cost sources.

250 mV switch saturation at 300 mA and 3.6V supply is not marvellous
(or poor) - accounts for a fair % of the low efficiency.
An external MOSFET part can have vastly better Rdson and no greater
cost overall. Footprint not much worse probably.

Where absolute efficiency is not essential it's compact and easy to
use with good features.


         Russell McMahon
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